Fast Fracture Evaluation of Steam Generator Channel Heads Considering High Carbon Macro-Segregation

Abstract The Fracture evaluation is important in the structural integrity analysis of nuclear equipment which is subjected to the effects of neutron irradiation. The increment of ductile and brittle transition temperature is mainly due to the neutron irradiation, thermal ageing and strain ageing. In addition to above these factors, the high carbon macro-segregation of low-alloy steels also increases the risk of fast fracture failure as the carbon positive macro-segregation will lead to the increasing transition temperature of low-alloy steels. In this work, a relationship between the carbon content and the increment of transition temperature is developed and is used to the fast fracture failure analysis of the highest carbon content region in steam generator channel head. Results show that ratio between the calculated stress intensity factor considering safety coefficient suggested by ASME design code and the critical stress intensity factor is less than one, which indicates a safe design for the highest carbon content region in steam generator channel head.

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Mechanical properties of low-alloy-steels with bainitic microstructures and varying carbon content

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/119/1/012005 ◽

2016 ◽

Vol 119 ◽

pp. 012005

Author(s):

A Weber ◽

J Klarner ◽

T Vogl ◽

R Schöngrundner ◽

G Sam ◽

...

Keyword(s):

Mechanical Properties ◽

Carbon Content ◽

Low Alloy Steels ◽

Alloy Steels

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Crack Tip Stress Analysis of the Steam Generator Dissimilar Steel Welded Joint under Residual Stress Field

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.795.451 ◽

2019 ◽

Vol 795 ◽

pp. 451-457

Author(s):

Bao Yin Zhu ◽

Xian Xi Xia ◽

He Zheng ◽

Guo Dong Zhang

Keyword(s):

Residual Stress ◽

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Stress Field ◽

Numerical Method ◽

Steam Generator ◽

Welded Joint ◽

Crack Tip ◽

Residual Stress Field

An typical mode of a structural integrity failure in dissimilar steel welded joints. This paper aims at studying crack tip stress of a steam generator dissimilar welded joint under residual stress field with the method of interaction integral and XFEM. Firstly, the corresponding weak form is obtained where the initial stress field is involved, which is the key step for the XFEM. Then, the interaction integral is applying to calculate the stress intensity factor. In addition, two simple benchmark problems are simulated in order to verify the precision of this numerical method. Finally, this numerical method is applying to calculate the crack tip SIF of the addressed problem. This study finds that the stress intensity factor increases firstly then decreases with the deepening of the crack. The main preponderance of this method concerns avoiding mesh update by take advantage of XFEM when simulating crack propagation, which could avoid double counting. In addition, our obtained results will contribute to the safe assessment of the nuclear power plant steam generator.

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Development of mechanical properties of structural high-carbon low-alloy steels through modified heat treatment

Journal of Materials Science ◽

10.1007/bf02397071 ◽

1989 ◽

Vol 24 (4) ◽

pp. 1357-1362 ◽

Cited By ~ 14

Author(s):

Yoshiyuki Tomita

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Low Alloy Steels ◽

High Carbon ◽

Alloy Steels ◽

Structural High

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Formation of Ultrafine Grained Ferrite by Warm Deformation of Tempered Lath Martensite in Low Alloy Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.557 ◽

2007 ◽

Vol 558-559 ◽

pp. 557-562 ◽

Cited By ~ 8

Author(s):

Behrang Poorganji ◽

Takuto Yamaguchi ◽

Tadashi Maki ◽

G. Miyamoto ◽

Tadashi Furuhara

Keyword(s):

Grain Size ◽

Carbon Content ◽

Volume Fraction ◽

Boundary Migration ◽

Lath Martensite ◽

Second Phase ◽

Low Alloy Steels ◽

Warm Deformation ◽

Alloy Steels ◽

Block Width

Microstructure change during warm deformation of tempered lath martensite in Fe-2mass%Mn-C alloys with different carbon contents in the range between 0.1 and 0.8mass%C was investigated. Specimens of the alloys after being quenched and tempered at 923K for 0.3ks were compressed by 50% with a strain rate varying from 10-3 to 10-4s-1 at 923K. EBSD analysis of the deformed microstructures has revealed that fine equiaxed ferrite (α) grains surrounded by high-angle boundaries are formed by dynamic recrystallization (DRX). As carbon content increases, the DRX α grain size decreases. This could be attributed to the change in volume fraction of the cementite (θ) phase as boundary dragging particles. The sub-micron θ particles can suppress the coarsening of the DRX α grains by exerting a pinning effect on grain boundary migration. Furthermore, the fraction of recrystallized region increases by increasing carbon content, presumably due to a decrease in the martensite block width as an initial α grain size and a larger volume fraction of hard second phase (θ) particles. Both of these should increase inhomogeneous plastic deformation which promotes the recrystallization. It seems that continuous DRX is responsible for the formation of ultrafine α grains in the tempered lath martensite.

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Development of mechanical properties of structural high-carbon low-alloy steels through modified heat treatment

Journal of Materials Science ◽

10.1007/pl00020220 ◽

1989 ◽

Vol 24 (4) ◽

pp. 1357-1362 ◽

Cited By ~ 6

Author(s):

Yoshiyuki Tomita

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Low Alloy Steels ◽

High Carbon ◽

Alloy Steels ◽

Structural High

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Effects of grain size on fracture toughness in transition temperature region of Mn–Mo–Ni low-alloy steels

Materials Science and Engineering A ◽

10.1016/s0921-5093(03)00344-7 ◽

2003 ◽

Vol 359 (1-2) ◽

pp. 198-209 ◽

Cited By ~ 50

Author(s):

Sangho Kim ◽

Sunghak Lee ◽

Bong Sang Lee

Keyword(s):

Fracture Toughness ◽

Grain Size ◽

Transition Temperature ◽

Temperature Region ◽

Low Alloy Steels ◽

Alloy Steels

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Fatigue Fracture, CTOD, and CVN Testing in Heat-Affected Zone of High Strength Low Alloy Steels

Advanced Models and Tools for Effective Decision Making Under Uncertainty and Risk Contexts - Advances in Business Strategy and Competitive Advantage ◽

10.4018/978-1-7998-3246-1.ch004 ◽

2021 ◽

pp. 90-156

Author(s):

Manuel Viseras Pico ◽

Rafael González-Palma ◽

María Carmen Carnero ◽

Carlos López-Escobar ◽

David Almorza

Keyword(s):

Growth Rate ◽

Stress Intensity Factor ◽

High Strength ◽

Crack Size ◽

Low Alloy Steels ◽

The North ◽

Martensitic Microstructure ◽

Input Control ◽

Alloy Steels ◽

The North Sea

High strength low alloy steels (HSLA) are currently used in large quantities for constructions in the North Sea and elsewhere. For success operation under such rigorous conditions, it is essential to ensure adequate weld metal toughness at temperatures of -10ºC or even lower is used. To comply with this high requirement, the heat input control is needed to avoid forming martensitic microstructure in high strength low alloy steels (HAZ) near to the fusion line during weldment cooling. This work carried out CTOD tests to ensure that, under welding conditions, the fatigue crack, toughness, hardness, and resilience in the HAZ are acceptable with the standards. Crack size in accordance with number cycles will be represented as the crack growth rate da/dN vs. stress intensity factor amplitude.

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